1. Field of the Invention
The present invention relates to a snowmobile capable of running on a snow field, with an engine as a drive source.
2. Description of Background Art
There have been made a variety of proposals as to the layout of apparatuses around an engine (the layout of a steering shaft and a silencer) in a snowmobile running by the power of the engine. See, for example Japanese Patent Laid-open No. Hei 7-228288.
FIG. 2 of Japanese Patent Laid-open No. Hei 7-228288 is a plan view showing the internal structure of a conventional snowmobile, in which symbol 1 denotes the snowmobile, symbol 14 denotes an engine, symbol 21 denotes a silencer, symbol 24 denotes an exhaust pipe, symbol 25 denotes a steering shaft, and symbol 26 denotes a steering handle.
In recent years, silencers have come to be larger and heavier for the purposes of configuring a 4-cycle engine and enhancing the silencing performance. When the silencer becomes larger and heavier, influences are exerted particularly on the turning performance, so that it becomes necessary to take it into account to maintain the left-right balance.
In Japanese Patent Laid-open No. Hei 7-228288, the silencer 21 is disposed on a lateral side of the vehicle body, so that if the silencer 21 is enlarged in size, it is impossible to secure a space in which to contain the silencer 21. Besides, when the silencer 21 is disposed on the front side, the silencer 21 would interfere with the steering shaft 25.
In connection with snowmobiles for running by the power of an engine, proposals have been made as to the step floors on which to put the rider's feet. See, for example, U.S. Pat. No. 6,446,744.
FIG. 28 of U.S. Pat. No. 6,446,744 is a perspective view of a vehicle body frame of a snowmobile according to the prior art.
The vehicle body frame is a member which comprises step floors 166, 168 on lateral sides of a lower portion of the frame, and comprises a plurality of anti-slip portions 426 (indicates plurality, here and hereinafter) on the surfaces of the step floors 166, 168.
FIG. 37 of U.S. Pat. No. 6,446,744 is a perspective view of the anti-slip portion, and is an enlarged illustration of one of the plurality of anti-slip portions 426.
The anti-slip portion 426 is composed of a projection portion 430, a rugged portion 432 provided at a tip end portion of the projection portion 430, a hole portion 428 provided adjacently to the projection portion 430, and a recessed portion 434 provided adjacently to the hole portion 428, and the rider's foot is placed on the rugged portion 432 to obtain an anti-slip effect.
However, since the step floor as a whole is a wide and flat structure, and leaves a room for improvement, for example, there is the problem that the optimum positioning of the foot is difficult to achieve when the rider rides in a standing pose.